This invention relates to processes and apparatus for the production of optical cables, that is to say cables incorporating one or more optical fibres within a protective cover, and relates especially to the production of such cables which are of the kind incorporating an extruded core of thermoplastics material having series of longitudinally extending channels, at least one of which accommodates one or more of said optical fibres, the core being surrounded in the completed cable, by an outer sheath.
Commonly the channels extend in a helical manner about the core axis, either in the form of a continuous helix or one in which the pitch of the helix is periodically reversed, the fibre or fibres being loosely accommodated within the respective channel or channels, which may either be completely closed or be formed as grooves in the periphery of the core. Hitherto the formation of the helical channels in the core has been effected by twisting the core while it is still in a softened condition after leaving the extruder, but in the case where the channels are provided by grooves in the periphery of the core this can give rise to difficulties in introducing the fibres into the grooves at some subsequent stage of manufacture.